Method and means for emitting signals with varying signal character



d- 1940- E. R; PARSBERG 2,219,017

METHOD AND IEANS. FOR EMITTING SIGNALS WITH VARYING SIGNAL CHARACTER Original Filed Dec. 22, 1932 INVEN OE WITNESS Erik fiobenfi az'sfieigg,

Patented Oct. 22, 1940 METHOD AND MEANS Foa EMITTING-SIG- NALS wrrn vmmc SIGNAL mm- ACTER Erik Robert Parsberg, ,Lidingo, near Stockholm, Sweden, assignor to American Gas Accumulator Company, Elizabeth, N. 1., a corporation of New Jersey Original application December 22, 1932, Serial No.

648,348. Divided and this application September 30, 1937, Serial No. 166,536. In Sweden December 24, 1931 3 Claims.

Application for Letters Patent was filed in Sweden December 24, 1931, and in the United States December 22, 1932, Serial No. 648,348. The present application is a division of United States application Serial No. 648,348, on which Patent No. 2,096,755 issued October 26, 1937.

It has become the general practice in arranging the illumination of air routes to use powerful revolving searchlights projecting beams of condensed light which sweep the horizon. When these beams of light sweep past a certain point, the impression obtained in the said point is that of a flashlight character, usually single' flash. The period between the separate flashes varies in length in difierent countries. In America, for instance, it is considered suflicient with one flash every ten seconds, whereas in Germany they have generally gone in for a period of about three seconds. If it is taken into consideration that it has been the practice for years to provide one flash every five seconds for marine tra-flic, which moves much slower, the conclusion is easily arrived at that for aviation the period should be quicker and not slower, and consequently that a period of three seconds would be more in accordance with the requirements of air trafiic.

Flashes at shorter intervals may be obtained by increasing the rotary speed of the apparatus or by dividing the available light energy into several beams. In both cases the efficiency of the beacon will be reduced. In the first case the light impression will be diminished, owing to the reduced duration of the flash (according to the Blondel and Rey law), while in the latter case the light eificiency of the beacon will be reduced by the division of the light energy.

The Frenchmen Blondel and Rey have scientifically proved that, in order to obtain a flashlight of a light range equivalent to that of fixed light, the light power of the flashlight must be larger-and consequently, in order to express its equivalent in terms of a fixed light, the light power of a flashlight must be multiplied by a factor which is less than 1. This factor is dependent on the duration of the flash and diminishes quickly as this is reduced. The factor in question is, for instance, approximately .2 for a flash of .03 second, .48 for a flash of .1 second, and rises to .84 for a flash of .3 second.

From this point of view, it would be advantageous in order to obtain a good light impression or a good signal effect, to have a long duration of the flash, which can be attained by increasing the width of the light beam or by reducing the rotary speed of the beacon. From the point of (Cl. 17'l352) view of light economy the first mentioned way of solving the question is not to be recommended. On the other hand, a reduction of the rotary speed will mean that the interval between the separate flashes will be longer. As stated 5 above, it is desirable that this interval should be comparatively-short. I

It is evident that the two requirements which thus present themselves, particularly in the technique of airway beacons, i. e.,- long duration of the flash on the one hand and short intervals between the separate flashes on the other, are at variance with each other, inasmuch as compli ance with one of the requirements requires a low' rotary speed, whereas the other requires high rotary speed of the beacon.

This invention refers to an arrangement by means of which the above-mentioned features are both attained simultaneously, the lens or reflector system of the beacon being so arranged as to oscillate with a revolving motion in such a way that the signal character of the beam or beams of light will be diflerent in different directions.

The intention with such a revolving motion is to improve the light impression-in certain sections of the revolution at the expense of the light impression in the other sections. When the beacon is intended as an airway beacon, the flying direction is suitably laid through the first mentioned sections, because the beacon light should be most visible in'that direction, whereas the other sections do not as a rule require full light power.

In one form of employing the invention, suitably arranged with two lens panels with 180 between the optical axis, the lens or reflector ap- .paratus is given an oscillating angular motion in the horizontal level, whereby the light beams will *sweep a certain section through which the flying direction is laid.

Fig. 1 shows a diagram of the light efliciency and the light character of a' beacon, the oscillating motion of which comprises an angle of approximately Fig. 2 is a diagram showing the light efliciency and the light character of a beacon, the oscillating motion'of which is greater than Fig. 3 shows a horizontal section of an arrangement of apparatus intended to provide for an oscillating motion of the lens system; and

Fig. 4 shows mechanism for. providing an oscillating motion through alarger angle.

Referring to Fig. l, the shadowed field inside curve e shows the light eificiency, whereas curve I M is a vector diagram by means of which the light character in different directions is easily read. If a vector g is drawn, this will intersect curve I in various points h, which correspond each to one flash. The space between these points is proportional to the eclipses between the flashes. In the case shown it is thus seen that two flashes h are obtained in succession, separated by a slightly longer dark period. The closer you come to the flying direction 13-4 or i i i. e., the sides of the revolving angle, the more the two flashes will melt into one long flash h On the other hand, in the direction of the bisectrix 1-9 of the angle a light character is obtained in which the flashes recur at equal intervals. In this way the character of the beacon can be read from the diagram in any direction.

The character of the beacon will thus alter during the oscillating motion, single flash character being obtained in the centre of the section. From the centre towards the edges the single-flash character changes gradually into a double-flash character that becomes more and more pronounced until the two flashes, following close on each other, melt into the long flash h. at the extreme edges. The aviator should naturally try to fly in the direction in which the last mentioned long single-flash character is seen.

A larger or smaller improvement of the light economy is obtained depending on the size of the angle or section that the beacon light has to sweep. If this angle is chosen to be 90 or of a revolution, for instance, as shown by Fig. 1, an amount of light is emitted within that angle which is four times larger than if the beacon were revolving 360, 1. e., a complete revolution. This increased amount of light may be utilized to improve the signal efiect of the beacon either by increasing the duration of the flash or by reducing the time between the flashes, or by both.

The sections of the revolution that are not swept by the said main beacon light lie outside the flying direction and do not require any lighting in normal flying. Should this be desired, however, a weaker secondary light can easily be arranged at k.

The revolving angle of the oscillating motion according to Fig. 1 can, if desired, be increased to 180. If this is done and .the flying direction is laid along the turning points of the revolving motion, single flash is obtained in the flying direction, whereas double-flash character is obtained as soon as the aviator deviates from the flying direction, as will be understood from the diagram in Fig. 1. In order to avoid collision of meeting aeroplanes, the aviator should in this case always keep to starboard of the beacon, i. e., the pilot should always keep inside the angle of the double-flash character, but as near the direction of the single-flash character as possible.

The revolving angle may also be larger than 180, as shown by Fig. 2, showing the light character of the two lens panels. The upper portion of Fig. 2, pertaining to one lens panel, is drawn with complete lines I, whereas the lower portion of Fig. 2, pertaining to the other lens panel, is marked with dotted lines m. From this diagram it is clear that in the angle a, which is swept by the light beams from both of the lens panels, the flashes will occur twice as frequently as in the other sections. If a radius is drawn within this angle, the following character is obtained: two flashes following close on each other--one darkperiod-two close flashes-etc. The flying direction is therefore suitably laid within this angle a.

If the flying route is laid along one of the legs of the said angle a and the opposing angles of two successive beacons are on opposite sides of a line joining these beacons, two aeroplanes coming from opposite directions cannot collide, provided that both aviators keep inside the angle, in which the close-double-flash character of the beacon in front of them is seen. From Fig. 2 it is also seen that the light efliciency curve n in this case will also be an ellipse.

Lights of the description in question make the use of special so-called course lights"unnecessary, because the aviator will notice an alteration in the flying character as soon as he deviates from the flying course.

The above-described forms of arranging the light may naturally also be used for maritime beacons, or for maritime and airway beacons combined.

Referring to the apparatus shown in Fig. 3, on the driving shaft 46 a cam disk 41 is placed, arranged in such a way as to guide an arm 49 secured on the shaft 48 of the lens system comprising Fresnel lenses I and 2', having a source of light therein. When the shaft 46 revolves the shaft 48 will in this way be turned back and forth over a certain angle. Constant angular speed may suitably be obtained if the cam disk 41 is shaped as an involute.

If the movement of the lens system is desired to comprise a larger angle than 90 an intermediate shaft 49a may be arranged, according to Fig. 4, between the cam disk 41 and the shaft 48, this intermediate shaft 49a being fitted with a cogged segment 5|! which engaged with a cogged wheel 5| on the shaft 48, the segment co-operating with the cam disk 41. By choosing a suitable relation between the gearing of the cogged segment 50 and the cogged wheel 5| the desired revolving angle of the lens apparatus is obtained.

In Fig. 3, the corresponding light diagram of which is shown in Fig. l, 12 is the lens for transmitting from the source of light the secondary light shown at k in the diagram.

Obviously the method of transmitting directed beams above mentioned can be used in connection with beams of all kinds. Here the use of beams of visible light has been shown, but it is assumed that radio beams or beams of other than visible light may be transmitted in. the same manner equally well.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In signaling apparatus, a source of radiant energy, projecting means for producing from the energy emitted by said source two oppositely directed primary beams and two oppositely directed primary beams and two oppositely directed secondary beams substantially at right angles to said primary beams and substantially in the plane of said primary beams, a support upon which said projecting means is oscillatably mounted, a continuously rotated driving shaft, a crank arm on said support, and a cam on said driving shaft for co-operating with said arm to oscillate said support through a pre-determined angle.

2. In signaling apparatus, a source of radiant energy, projecting means for producing two oppositely directed beams from the energy emitted by said source, a support upon which said projecting means is oscillatably mounted, a continuously rotated driving shaft, a driven shaft secured to said support, an intermediate shaft between said driving shaft and said driven shaft, a cog wheel on said driven shaft, a cog segment on said intermediate shaft, and a cam on said driving shaft for co-operating with said segment to oscillate said support through a predetermined angle.

3. In signaling apparatus, a source of radiant energy, projecting means for producing from the energy emitted by said source two oppositely directed primary beams and two oppositely directed secondary beams substantially at right angles to said primary beams and substantially in the plane of said primary beams, a support upon which said projecting means is oscillatably mounted, and mechanism for oscillating said support to swing each of said beams simultaneously through a pre-determined angle in said CERTIFICATE OF CORRECTION. Patent No. 2,219,017. October 22, 1 b0,.

ERIK ROBERT PARSBERG.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, second column, lines 60 a wleim 1, strike out the words and two opposite- 1y directed primary beams"; and that the said Letters Patent should be read with this correction therein that the same 'may conform to the record of the case in the Patent Office.

Signed and sealed this 19th day of November, A. D. 191w.

Henry Van Arsdal (Seal) Acting Commissioner of Patents. 

